To shew how far-reaching some of the discussions are, attention may be directed to the fact that in this particular argument, much turns upon the nature of the implements found with the 'southern fauna' at Taubach (_v. ante_ Chapters II and III). If the implements are of Mousterian type, they support Professor Penck's view, for the 'warm Mousterian' sought by him will thus be found: but if the type is Chellean, the arguments of Professor Boule are notably reinforced. (6) The position assigned to one stage in the series of implements will affect all the rest. Professor Penck's view has been attacked with vigour and also with great effect, on account of the position he allots to the type of Solutré. The consensus of opinion regarding the position of Solutré (_i.e._ its typical implements) is very extensive and quite definite. In effect, the type of Solutré is assigned to the newer (_jüngerer_) löss deposits. But these are also widely recognised as entirely post-glacial. Moreover in the last few years, the excavations in these particular löss-deposits in Lower Austria have not only confirmed that opinion, but have also revealed there the presence of Aurignacian implements, which closely follow those of Mousterian type. Professor Penck's scheme seems therefore to carry the Solutréan implements too far back. The attempt to overcome this objection by attributing an earlier (? inter-glacial) age to the special variety of löss in question, has not been attended with conspicuous success. Such are the main considerations upon which the decision has been taken in favour of Professor Boule's chronological scale. But when such an authority as Professor Sollas[46] (1908) is undecided, an amateur must not attempt to ignore the difficulties to be met. And while it is expedient to arrive at a final judgment, yet, in these controversies, the tendency is very marked to allow theory to run too far ahead of fact. Facts of the following kind are hard to reconcile with the schemes just described. (i) A Mousterian type of implement is recorded by Commont from the later (younger) löss of the third terrace at S. Acheul. According to the theory, the type of Solutré, and not of Le Moustier, should have occurred, (ii) In this country at least, an admixture of 'northern' and 'southern' animals in a single deposit, has been demonstrated not infrequently, as in Italy also (Torre della Scalea, Cosenza). (iii) Professor Boyd Dawkins[47] (1910) insists upon the occurrence of Chellean, Acheulean, and Mousterian implements in one and the same British river deposit. Consequently the distinction of a northern from a southern fauna may yet prove to be destitute of sound foundations. Many years ago, Saporta pointed out instances of regions with a sub-tropical climate actually adjacent to glacial areas. This subject has fortunately now the advantage of the attention and criticism provided by such talented observers as Mr Hinton, Professor Laville, and Professor Schmidt.